"We are united in our mission to transform Labour so that, once again, we stand up for the hardworking majority who play by the rules and want a less divided and more prosperous Britain. I know we have a lot of work to do. The journey starts today."

Greenpeace's executive director, John Sauven, said he hoped the outcome would give Labour an environmental push and hold the coalition to account.

He said: "We have high hopes the man who brought an end to the era of coal-fired power stations with unlimited emissions will be the right man to hold Cameron's 'greenest government ever' to their promises."